Why is this UV Map face not displaying correctly?
it's becouse your triangle is rotated. Let's i describe it in image:



your vertex number 1 is on position of vertex 3, n.2 on position of 1, n.3 on pos. 2.

so it look like all vertex on right place, but this places are wrong:



Selecting in mesh uv sync mode displays that one vertex is on different positions in UV.